This invention relates to a method for detecting color as an indicator of the presence of a contaminant or an undesired component in animal feeds and pharmaceutical preparations and, more particularly, to a method for detecting the presence of a sulfonamide or other undesired component in such feeds or pharmaceutical preparations.
As is known, the Food and Drug Administration and the U.S. Department of Agriculture have established acceptable levels for antibiotic sulfonamides ("sulfas"), such as sulfamethazine, in pork. Nevertheless, the problem of illegal sulfa drug residue levels in pork has persisted and it is difficult to monitor the presence of unacceptable levels of sulfas in premixed animal feeds and to clean equipment which has been used in processing feeds with unacceptable levels of sulfas since these compounds cling to metal equipment and readily contaminate other feeds processed therein. According to government regulations, many sulfas may not be added to animal feed since such use may result in residue violations in pork and other meat products. Sulfas in combination with other antibiotics have been approved for use in swine feeds and the approved feed level for sulfas is generally the effective amount hogs can handle without producing illegal residues when a required withdrawal time is observed.
Sulfa violations have heretofore been difficult to detect and there has been no practical and convenient means available for determining whether animal feeds contain even traces of sulfas and/or in amounts which are within acceptable levels. Also, the regulatory agencies involved have not been equipped with techniques for monitoring the adequacy of feed mixing procedures or the cleanliness of equipment to insure that sulfas are maintained at acceptable levels in animal feeds. Similar problems are encountered in the case of other preparations, such as various pharmaceutical preparations, where it is important to insure that certain contaminants or impurities whose presence may be deleterious are not contained in the preparations.
Accordingly, there has been a continuing need for the development of practical and convenient means for detecting and monitoring the presence of sulfonamides and other compounds in animal feeds and pharmaceutical preparations for human or veterinary use and on processing equipment.